A system for an adaptive, mechanical tolerance compensation acting in the lift direction for a path transducer of a piezoelectric actuator for a fuel injector is described in published European Patent document EP 0 477 400. In the process, the actuator lift is transmitted via a hydraulic chamber. The hydraulic chamber has a defined leak having a defined leakage rate. The actuator lift is introduced into the hydraulic chamber via a master piston and transmitted to an element to be driven via a slave piston, for example, a valve needle of a fuel injector.
Guided in the master piston is a slave piston, which also seals the master piston and in this way forms the hydraulic chamber. Arranged in the hydraulic chamber is a spring which presses the master piston and the slave piston apart. When the actuator transmits a lifting movement to the master cylinder, the pressure of a hydraulic fluid in the hydraulic chamber transmits this lifting movement to the slave piston since the hydraulic fluid in the hydraulic chamber is not compressible and only a small portion of the hydraulic fluid is able to escape through the ring gap during the short duration of a lift. In the rest phase, when the actuator exerts no pressure force on the master cylinder, the spring pushes the slave piston out of the cylinder and, due to the generated vacuum pressure, the hydraulic fluid penetrates the hydraulic chamber and replenishes it via the annular gap. In this way, the hydraulic coupler automatically adapts to linear deformations and pressure-related expansions of a fuel injector. The hydraulic medium is sealed via sealing rings.
In addition, fuel injectors are known from the related art, which seal hydraulic media by flexible sections in the shape of a corrugated tube or convoluted bellows, for example, and preload the hydraulic medium by an elastic design of the flexible section.
Disadvantageous in this known related art is that the preloading by the flexible section changes during the service life of the fuel injector in a disadvantageous manner, the coupler has a complex design and is able to be produced only at great expense due to the many individual components of the coupler.